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diff --git a/tran/biquadfilt.alg b/tran/biquadfilt.alg
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+; general order-2 IIR filter.
+; a0 is assumed to be unity.
+; for a1 and a2, our sign convention is opposite to Matlab's.
+
+(SNDBIQUAD-ALG
+(NAME "biquadfilt")
+(LISPNAME "biquad")
+(ARGUMENTS ("sound_type" "s") 
+        ("double" "b0") ("double" "b1") ("double" "b2") 
+                         ("double" "a1") ("double" "a2")
+        ("double" "z1init") ("double" "z2init"))
+(START (MIN s))
+(TERMINATE (MIN s))
+(LOGICAL-STOP (MIN s))
+(STATE	("double" "z1" "z1init")
+        ("double" "z2" "z2init")
+        ("double" "b0" "b0")
+        ("double" "b1" "b1")
+        ("double" "b2" "b2")
+        ("double" "a1" "a1")
+        ("double" "a2" "a2"))
+(CONSTANT "b0" "b1" "b2" "a1" "a2")
+(INNER-LOOP-LOCALS "double z0;")
+(INNER-LOOP "	z0 = s + a1*z1 + a2*z2;
+                    output = (sample_type) (z0*b0 + z1*b1 + z2*b2);
+                    z2 = z1; z1 = z0;")
+)
+